Hybrid, coaxial nanowire photovoltaic cells, consisting of a crystalline silicon (c-Si) core and an amorphous silicon (a-Si) shell are an appealing idea. In such c-Si/a-Si coaxial photovoltaic cells, the c-Si core can act as an efficient charge collector to compensate for short charge diffusion lengths of a-Si, whereas the a-Si shell can be used as an excellent energy absorber to overcome poor light absorption of c-Si. As a matter of fact, a few groups [Nature 449 885 (2007); Nano Lett. 10 4093 (2010)] have made such coaxial nanostructures and tested the great light absorption nature of the devices. However, the underlying physics of light absorption in the coaxial nanowire system requires further investigation.
http://nanotechweb.org/cws/article/lab/45409